The invention relates to a piston pump for a vehicle brake system.
Many such piston pumps are known. The piston pump known from German Patent Disclosure DE 41 07 979 A1 can be taken as an example. The known piston pump has a piston which is axially displaceably guided in a bush that is inserted into a cylinder bore of a pump housing. A closure element in the form of a cap is inserted into the cylinder bore and closes it in pressure-tight fashion. A disadvantage is that the bush and the closure element have to be inserted into the cylinder bore in separate steps.
In the piston pump of the invention, the closure element is joined to the bush and there is radial play between the closure element and the bush. The bush is inserted, jointly with the closure element secured to it, into the cylinder bore in a single step, and is secured in the cylinder bore and sealed off in pressure-tight fashion by caulking, for example. The piston pump of the invention has the advantage that it is preassembled in final form before being inserted into the pump housing, and forms a compact, easily manipulated, and sturdy component unit. A mechanically overdefined mounting of the bush, with the closure element secured to it, in the cylinder bore of the pump housing is avoided. This prevents strains that could be caused by an alignment error between the closure element and the bush. The mechanical strength of the mounting in the cylinder bore is increased, as is the security against leaking.
The piston pump is intended in particular as a pump in a brake system of a vehicle and is used in controlling the pressure in wheel brake cylinders. Depending on the type of brake system, the abbreviations ABS, ASR, FDR and EHB are used for such brake systems. In the brake system, the pump serves for instance to return brake fluid from one or more wheel brake cylinders to a master cylinder (ABS) and/or to pump brake fluid out of a supply container into one or more wheel brake cylinders (ASR or FDR or EHB). The pump is needed for instance in a brake system with wheel slip control (ABS or ASR) and/or a brake system serving as a steering aid (FDR) and/or an electrohydraulic brake system (EHB). With wheel slip control (ABS or ASR), locking of the wheels of the vehicle during a braking event involving strong pressure on the brake pedal (ABS) and/or spinning of the driven wheels of the vehicle in the event of strong pressure on the gas pedal (ASR) can for instance be prevented. In a brake system serving as a steering aid (FDR), a brake pressure is built up in one or more wheel brake cylinders independently of an actuation of the brake pedal or gas pedal, for instance to prevent the vehicle from breaking out of the lane desired by the driver. The pump can also be used in an electrohydraulic brake system (EHB), in which the pump pumps the brake fluid into the wheel brake cylinder or wheel brake cylinders if an electric brake pedal sensor detects an actuation of the brake pedal, or in which the pump is used to fill a reservoir of the brake system.